Methods for epitaxial silicon growth

ABSTRACT

Methods of cleaning substrates and growing epitaxial silicon thereon are provided. Wafers are exposed to a plasma for a sufficient time prior to epitaxial silicon growth, in order to clean the wafers. The methods exhibit enhanced selectivity and reduced lateral growth of epitaxial silicon. The wafers may have dielectric areas that are passivated by the exposure of the wafer to a plasma.

BACKGROUND OF THE INVENTION

Epitaxial silicon is used in a variety of semiconductor devices when apure silicon layer is required. Epitaxial silicon is generally grown ona substrate and exhibits the same crystal structure as the substrate onwhich it is grown. Epitaxial silicon layers may have their doping typeor concentration controlled independently from the substrate on whichthe layers are grown. Generally, the substrate on which epitaxialsilicon is to be grown must be cleaned prior to the growth to removeimpurities and ensure that the epitaxial silicon layer is of a highquality.

One approach to cleaning substrates prior to epitaxial silicon growth isto wash the substrate using hydrofluoric acid and to subsequentlyhydrogen bake the substrate at high temperatures. However, epitaxialsilicon growth on silicon areas cleaned in this manner may exhibit ahigh degree of unwanted lateral growth. Additionally, dielectric layersthat are subsequently exposed to epitaxial silicon growth by chemicalvapor deposition may exhibit unwanted epitaxial silicon growth in areasof nucleation in the dielectric layers. Thus, the selectivity of theepitaxial silicon growth process may be low.

Therefore, there remains a need in the art for epitaxial silicon growthmethods that do not exhibit a high degree of lateral growth.Additionally, there remains a need in the art for epitaxial silicongrowth methods that are selective.

SUMMARY OF THE INVENTION

These needs are addressed by embodiments of the present invention thatprovide substrate cleaning and epitaxial silicon growth methods.

In accordance with an embodiment of the present invention, a method ofcleaning a semiconductor surface is provided. The method comprises;providing a wafer, wherein the wafer has an upper surface, and whereinthe wafer has a silicon area on the upper surface; forming a plasma froma gas flow, wherein the gas flow comprises an etchant gas; and exposingthe upper surface of the wafer to the plasma. The exposure of the uppersurface of the wafer to the plasma cleans the upper surface and rendersthe silicon area suitable for subsequent epitaxial silicon growth.

In accordance with another embodiment of the present invention, a methodof growing epitaxial silicon is provided. The method comprises providinga wafer, wherein the wafer has an upper surface, and wherein the waferhas a silicon area on the upper surface. The method further comprisesforming a RF plasma from a gas flow, wherein the gas flow comprises anetchant gas, and exposing the upper surface of the wafer to the RFplasma. The exposure of the upper surface of the wafer to the RF plasmarenders the silicon area suitable for epitaxial silicon growth. Themethod also comprises growing epitaxial silicon on the silicon areasubsequent to the exposure of the upper surface of the wafer to the RFplasma.

In accordance with yet another embodiment of the present invention, amethod of growing epitaxial silicon is provided. The method comprisesproviding a wafer. The wafer has an upper surface, and the wafer has afirst silicon area on the upper surface. Additionally, the wafer has afirst dielectric area on the upper surface. The method further comprisesforming a RF plasma from a gas flow, wherein the gas flow comprises atleast one etchant gas. The method comprises exposing the upper surfaceof the wafer to the RF plasma. The exposure of the upper surface of thewafer to the RF plasma renders the first silicon area suitable forepitaxial silicon growth. The method also comprises growing epitaxialsilicon on the first silicon area subsequent to the exposure of theupper surface of the wafer to the RF plasma. The epitaxial silicongrowth exhibits selectivity of growth on the first silicon area over thefirst dielectric area, and the selectivity of growth is enhanced by theexposure of the upper surface of the wafer to the RF plasma.

In accordance with another embodiment of the present invention, a methodof growing epitaxial silicon is provided. The method comprises providinga wafer. The wafer has an upper surface. The wafer has a first siliconarea on the upper surface, and the wafer has a first dielectric area onthe upper surface. The method comprises forming a RF plasma from a gasflow, wherein the gas flow comprises at least one etchant gas. Themethod further comprises exposing the upper surface of the wafer to theRF plasma, wherein the exposure of the upper surface of the wafer to theRF plasma renders the first silicon area suitable for epitaxial silicongrowth. The method comprises growing epitaxial silicon on the firstsilicon area subsequent to the exposure of the upper surface of thewafer to the RF plasma. The epitaxial silicon grows at a lateral growthrate and a vertical growth rate. The lateral growth rate of theepitaxial silicon is reduced relative to the vertical growth rate by theexposure of the upper surface of the wafer to the RF plasma.

In accordance with another embodiment of the present invention, a methodof growing epitaxial silicon is provided. The method comprises cleaninga surface having a dielectric area adjacent to a silicon area with a RFplasma formed from a gas flow having an etchant gas and growingepitaxial silicon on the cleaned surface. The epitaxial silicon growthexhibits selectivity of growth on the silicon area over the dielectricarea, and the selectivity of growth is enhanced by the cleaning of thesurface. The epitaxial silicon grows at a lateral growth rate and avertical growth rate over the silicon area, and the lateral growth rateof the epitaxial silicon is reduced relative to the vertical growth rateby the cleaning of the surface.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIGS. 1A–1B are cross sectional views of epitaxial silicon growth inaccordance with an embodiment of the present invention.

FIG. 2 is a flow diagram of process steps for epitaxial silicon growthin accordance with the embodiments of the present invention.

FIGS. 3A–3B are cross sectional views of epitaxial silicon growth inaccordance with another embodiment of the present invention.

FIGS. 4A–4B are cross sectional views of epitaxial silicon growth inaccordance with yet another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to methods of cleaning substrates andgrowing epitaxial silicon thereon. The methods expose the substrates toa plasma prior to epitaxial silicon growth. The methods exhibit a highdegree of selectivity and a low degree of lateral growth of epitaxialsilicon layers.

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings that form a part hereof,and in which is shown by way of illustration, and not by way oflimitation, specific preferred embodiments in which the invention may bepracticed. It is to be understood that other embodiments may be utilizedand that logical, mechanical, and electrical changes may be made withoutdeparting from the spirit and scope of the present invention. In thedrawings, like numerals describe substantially similar componentsthroughout the several views.

Referring to FIGS. 1A, 1B, and 2, a method of growing epitaxial siliconis illustrated. The method includes the step 20 of providing a wafer 10.For purposes of defining and describing the present invention, the term“wafer” is defined to mean any composition or construction comprisingsemiconductive material, including, but not limited to, bulksemiconductive material such as a semiconductive wafer, either alone orin assemblies comprising other materials thereon, and semiconductivematerial layers, either alone or in assemblies comprising othermaterials. The wafer 10 generally has an upper surface 12 and a lowersurface 14. Additionally, the wafer 10 has a silicon area 16 on theupper surface 12. For purposes of defining and describing the presentinvention, the term “silicon area” is defined to mean an area containingsilicon or polysilicon, whether doped or undoped.

A plasma is formed from a gas flow in step 22, and upper surface 12 ofthe wafer 10 is exposed to the plasma in step 24. Generally, the plasmais a radio frequency (RF) plasma that is formed by applying an RF powerto the gas flow. The gas flow contains at least one etchant gas. Theetchant gas is selected to contain a species that may be ionized in theplasma and that may etch the wafer 10. For example, the etchant gas maybe a gas containing a halogen. Suitable etchant gases include, but arenot limited to F₂, Cl₂, CF₄, SF₆, and the like. The RF plasma may beformed in a processing chamber, and the wafer 10 may be provided in theprocessing chamber during steps 20, 22, and 24. For example, the wafer10 may be provided in a single wafer processing chamber. Alternatively,the wafer 10 may be provided in a batch processing chamber. Subsequentepitaxial silicon growth, as described hereinafter, may be carried outin the same or a different processing chamber as the exposure of thewafer 10 to the plasma in step 24. Generally, the epitaxial silicongrowth is carried out in the same processing chamber.

The RF plasma is generally a low power plasma that etches the uppersurface 12 of the wafer and removes unwanted contaminants and oxide fromthe upper surface 12. For example, when SF₆ is used as the gas flow, theRF power may be between about 300 to about 450 W. The gas flow may havea flow rate of between about 30 to about 40 standard cubic centimetersper minute (sccm). The background pressure may be between about 10⁻⁶ toabout 10⁻⁸ Torr. The wafer 10 may be exposed to the RF plasma forbetween about 1 second to about 2 minutes.

Once the upper surface 12 of the wafer 10 has been exposed to the plasmafor a sufficient time, the upper surface 12 is cleaned, and the siliconareas 16 are generally rendered suitable for subsequent epitaxialsilicon growth. It will be understood that the upper surface 12 may havea plurality of silicon areas 16, and the exposure of the wafer 10 to theplasma will render the plurality of silicon areas suitable forsubsequent epitaxial silicon growth. After the wafer 10 has been exposedto the plasma, epitaxial silicon 18 may be grown on the silicon area 16as illustrated by step 26. The epitaxial silicon 18 may be grown usingany suitable growth method. For example, the epitaxial silicon 18 may begrown using a suitable chemical vapor deposition (CVD) method. Theepitaxial silicon 18 is generally of high quality. It will be understoodthat “epitaxial silicon” may be used to refer to epitaxial silicon orepitaxial polysilicon that is grown on silicon or polysilicon areasrespectively.

Referring to FIGS. 2, 3A and 3B, a method of growing epitaxial siliconis illustrated. The method includes the step 20 of providing a wafer 10.The wafer 10 has an upper surface 12. The wafer 10 has at least onesilicon area 16 on the upper surface 12, and the wafer 10 has at leastone dielectric area 30 on the upper surface 12. The dielectric areas 30may be any suitable dielectric. For example, the dielectric areas 30 maybe silicon oxide, silicon nitride, or combinations thereof. A RF plasmais formed in step 22 as described herein, and the upper surface 12 ofthe wafer 10 is exposed to the plasma in step 24. The exposure of theupper surface 12 of the wafer 10 to the plasma in step 24 renders thesilicon areas 16 suitable for epitaxial silicon growth. Additionally,the exposure of the upper surface of the wafer 10 to the plasma in step24 passivates a surface 32 of the dielectric areas 30.

Epitaxial silicon 18 is grown on the silicon areas 16 as shown in step26 subsequent to step 24. The epitaxial silicon 18 is grown in aselective manner because it generally grows only the silicon areas 16 onthe upper surface 12 of the wafer 10 and does not grow significantly onthe dielectric areas 30. Epitaxial silicon growth on the dielectricareas 30 is substantially prevented by the exposure of the upper surface12 of the wafer 10 to the plasma because the surface 32 has beenpassivated, and epitaxial silicon does not grow as readily on thesurface of the passivated dielectric because nucleation centers may notform as readily during growth. Thus, the selectivity of the epitaxialsilicon growth method is increased by the exposure of the wafer 10 tothe plasma in step 24. The dielectric areas 30 may serve as mask areasthat may be subsequently removed in later processing steps as desired.

Referring to FIGS. 2, 4A, and 4B, a method of growing epitaxial siliconis illustrated. The method includes providing a wafer 10 in step 20, andthe wafer 10 has an upper surface 12. The wafer 10 has at least onesilicon area 16 on the upper surface 12, and the wafer 10 has at leastone dielectric area 30 on the upper surface 12. The dielectric area 30is adjacent to the silicon area 16. A RF plasma is formed in step 22,and the upper surface 12 of the wafer 10 is exposed to the RF plasma instep 24. The silicon area 16 is rendered suitable for epitaxial silicongrowth by the exposure of the upper surface 12 to the plasma.

Epitaxial silicon 18 is grown on the silicon area 16 in step 26subsequent to step 24. The epitaxial silicon 18 grows in a verticaldirection 34 and in a lateral direction 36. The growth in the verticaldirection 34 exhibits a vertical growth rate, and the growth in thelateral direction 36 exhibits a lateral growth rate. The lateral growthrate is reduced relative to the vertical growth rate by the exposure ofthe upper surface 12 of the wafer 10 to the RF plasma. It is believedthat the condition of the surface bonds of the dielectric area 30 arechanged by the RF plasma, and the lateral growth 36 of the epitaxialsilicon is thus inhibited.

Steps 22 and 24 may be controlled in any suitable manner to provide adesired reduction in the lateral growth rate when the epitaxial silicon18 is grown in step 26. For example, the lateral growth rate may have aratio to the vertical growth rate of between about 1:1 to about 1:8.More generally, the lateral growth rate may have a ratio to the verticalgrowth rate of between about 1:4 to about 1:8. Thus, lateral growth ofthe epitaxial silicon 18 may be reduced over the adjacent dielectricarea 30. It will be understood that the wafer 10 may have a plurality ofsilicon areas 16 and a plurality of dielectric areas 30 on an uppersurface 12.

In order that the invention may be more readily understood, reference ismade to the following examples, which are intended to be illustrative ofthe invention, but are not intended to be limiting in scope.

EXAMPLE 1

A wafer having silicon areas and silicon nitride areas on an uppersurface was exposed to a RF plasma formed from an SF₆ gas flow flowingat 40 sccm. The RF power was 300 W, and the wafer was exposed to theplasma for 60 seconds.

Epitaxial silicon was subsequently grown on the silicon areas. Theepitaxial silicon was grown by a SiH₆, Cl₂, and H₂ gas flow present witha 10⁻⁸ Torr background pressure. The growth was continued for betweenabout 5 to about 25 minutes in order to achieve a desired thickness ofepitaxial silicon. The nitride areas did not exhibit significantepitaxial silicon growth, and it was apparent that the RF plasma hadpassivated the surface of the nitride.

EXAMPLE 2

A wafer having polysilicon areas and silicon nitride areas on an uppersurface was exposed to a RF plasma formed from an SF₆ gas flow flowingat 40 sccm. The RF power was 300 W, and the wafer was exposed to theplasma for 60 seconds.

Epitaxial polysilicon was subsequently grown on the silicon areas. Theepitaxial silicon was grown by a SiH₆, Cl₂, and H₂ gas flow present witha 10⁻⁸ Torr background pressure. The growth was continued for betweenabout 5 to about 25 minutes in order to achieve a desired thickness ofepitaxial polysilicon. The nitride areas did not exhibit significantepitaxial polysilicon growth, and it was apparent that the RF plasma hadpassivated the surface of the nitride.

EXAMPLE 3

A wafer having silicon areas and silicon oxide areas on an upper surfacewas exposed to a RF plasma for 60 seconds. The plasma was formed from a40 sccm gas flow of SF₆, and the RF power was 300 W.

Epitaxial silicon was grown on the silicon areas by a SiH₆, Cl₂, and H₂gas flow present with a 10⁻⁸ Torr background pressure. The growth wascontinued for between about 5 to about 25 minutes in order to achieve adesired thickness of epitaxial silicon. The epitaxial silicon exhibiteda lateral growth rate to vertical growth rate ratio of about 1:4, asmeasured by comparing the height of the vertical growth to the width ofthe lateral growth.

It will be apparent to those skilled in the art that various changes maybe made without departing from the scope of the invention, which is notto be considered limited to what is described in the specification.

1. A method of cleaning a semiconductor surface, comprising: providing awafer, wherein said wafer has on upper surface, and wherein said waferhas at least one silicon area and at least one dielectric area on saidupper surface; forming a plasma from a gas flow, wherein said gas flowcomprises an etchant gas; and exposing said upper surface of said waferto said plasma, wherein said exposure of said upper surface of saidwafer to said plasma cleans said upper surface and renders said at leastone silicon area suitable for subsequent epitaxial silicon growth. 2.The method as claimed in claim 1 wherein said upper surface of saidwafer has a plurality of silicon areas thereon, and wherein saidexposure of said wafer to said plasma renders said plurality of siliconareas suitable far subsequent epitaxial silicon growth.
 3. A method ofgrowing epitaxial silicon, comprising: providing a wafer, wherein saidwafer has an upper surface, and wherein said wafer has at least onesilicon area and at least one dielectric area on said upper surface;forming a RF plasma from a gas flow, wherein said gas flow comprises anenchants gas; exposing said upper surface of said wafer to said RFplasma, wherein said exposure of said upper surface of said wafer tosaid RF plasma renders said at least one silicon area suitable forepitaxial silicon growth; and growing epitaxial silicon on said at leastone silicon area subsequent to said exposure of said upper surface ofsaid wafer to said RF plasma.
 4. The method as claimed in claim 3wherein said etchant gas comprises a gas containing a halogen.
 5. Themethod as claimed in claim 3 wherein said etchant gas comprises SF₆. 6.The method as claimed in claim 5 wherein said etchant gas has a gas flowrate of between about 30 to about 40 sccm.
 7. The method as claimed inclaim 5 wherein said RF plasma is formed using an RF power of betweenabout 300 to about 450 W.
 8. The method as claimed in claim 5 whereinsaid upper surface of said wafer is exposed to said RF plasma for about1 second to about 2 minutes.
 9. A method of growing epitaxial silicon,comprising: providing a wafer in a processing chamber, wherein saidwafer has an upper surface, and wherein said wafer has a silicon area onsaid upper surface; forming a RF plasma from a gas flow, wherein saidgas flow comprises an etchant gas, and wherein said RF plasma is formedin said processing chamber; exposing said upper surface of said wafer tosaid RF plasma in said processing chamber, wherein said exposure of saidupper surface of said wafer to said RF plasma renders said silicon areasuitable for epitaxial silicon growth; and growing epitaxial silicon onsaid silicon area subsequent to said exposure of said upper surface ofsaid wafer to said RF plasma, wherein said epitaxial silicon is grown insaid processing chamber.
 10. A method of growing epitaxial silicon,comprising: providing a wafer, wherein: said wafer baa an upper surface;said wafer has a first silicon area on said upper surface; and saidwafer has a first dielectric area on said upper surface; forming a RFplasma from a gas flow, wherein said gas flow comprises at least oneetchant gas; exposing said upper surface of said wafer to said RFplasma, wherein said exposure of said upper surface of said wafer tosaid RF plasma renders said first silicon area suitable for epitaxialsilicon growth; growing epitaxial silicon on said first silicon areasubsequent to said exposure of said upper surface of said wafer to saidRF plasma, wherein: said epitaxial silicon growth exhibits selectivityof growth on said first silicon area over said first dielectric area;and said selectivity of growth is enhanced by said exposure of saidupper surface of said wafer to said RF plasma.
 11. A method of growingepitaxial silicon, comprising: providing a wafer, wherein: said waferhas an upper surface; said wafer has a first silicon area on said uppersurface; said wafer has a first dielectric area on said upper surface;and said first dielectric area has a surface; forming a RF plasma from agas flow, wherein said gas flow comprises at least one etchant gas;exposing said upper surface of said wafer to said RF plasma, whereinsaid exposure of said upper surface of said wafer to said RF plasmarenders said first silicon area suitable for epitaxial silicon growth;said exposure of said upper surface of said wafer to said RF plasmapassivates said surface of said first dielectric area; selectivelygrowing epitaxial silicon on said first silicon area subsequent to saidexposure of said upper surface of said wafer to said RF plasma.
 12. Themethod as claimed in claim 11 wherein said first dielectric areacomprises a mask area.
 13. The method as claimed in claim 11 whereinsaid dielectric comprises silicon oxide.
 14. The method as claimed inclaim 11 wherein said dielectric comprises silicon nitride.
 15. Themethod as claimed in claim 11 wherein said first silicon area comprisesa polysilicon area.
 16. The method as claimed in claim 11 wherein saidfirst silicon area comprises a silicon area.
 17. The method as claimedin claim 11 wherein said upper surface of said wafer comprises aplurality of silicon areas, and wherein said upper surface of said wafercomprises a plurality of dielectric areas.
 18. A method of growingepitaxial silicon, comprising: providing a wafer, wherein: said waferhas an upper surface; said wafer has a first silicon area on said uppersurface; said wafer has a first dielectric area on said upper surface;and said first dielectric area has a surface; forming a RF plasma from agas flow, wherein said gas flow comprises at least one etchant gas;exposing said upper surface of said wafer to said RF plasma, whereinsaid exposure of said upper surface of said wafer to said RF plasmarenders said first silicon area suitable for epitaxial silicon growth;said exposure of said upper surface of said wafer to said RF plasmapassivates said surface of said first dielectric area; selectivelygrowing epitaxial silicon on said first silicon area subsequent to saidexposure of said upper surface of said wafer to said RF plasma, whereinsaid epitaxial silicon growth on said first dielectric area issubstantially prevented by said exposure of said upper surface of saidwafer to said RF plasma.
 19. A method of growing epitaxial silicon,comprising: providing a wafer, wherein: said wafer has an upper surface;said wafer has a first silicon area on said upper surface; and saidwafer has a first dielectric area on said upper surface; forming a RFplasma from a gas flow, wherein said gas flow comprises at least oneetchant gas; exposing said upper surface of said wafer to said RFplasma, wherein said exposure of said upper surface of said wafer tosaid RF plasma renders said first silicon area suitable for epitaxialsilicon growth; growing epitaxial silicon on said first silicon areasubsequent to said exposure of said upper surface of said wafer to saidRF plasma, wherein: said epitaxial silicon grows at a lateral growthrate and a vertical growth rate; and said lateral growth rate of saidepitaxial silicon is reduced relative to said vertical growth rate bysaid exposure of said upper surface of said wafer to said RF plasma. 20.A method of growing epitaxial silicon, comprising: providing a wafer,wherein: said wafer has an upper surface and a lower surface; said waferhas a first silicon area on said upper surface; and said wafer has afirst dielectric area on said upper surface adjacent to said firstsilicon area, forming a RF plasma from a gas flow, wherein said gas flowcomprises at least one etchant gas; exposing said upper surface of saidwafer to said RF plasma, wherein said exposure of said upper surface ofsaid wafer to said RF plasma renders said first silicon area suitablefor epitaxial silicon growth; growing epitaxial silicon on said firstsilicon area subsequent to said exposure of said upper surface of saidwafer to said RF plasma, wherein: said epitaxial silicon grows at alateral growth rate and a vertical growth rate; and said lateral growthrate of said epitaxial silicon is reduced relative to said verticalgrowth rate by said exposure of said upper surface of said wafer to saidRF plasma.
 21. A method of growing epitaxial silicon, comprising:providing a wafer, wherein: said wafer has an upper surface; said waferhas a first silicon area on said upper surface; and said wafer has afirst dielectric area on said upper surface adjacent to said firstsilicon area; forming a RF plasma from a gas flow, wherein said gas flowcomprises at least one etchant gas; exposing said upper surface of saidwafer to said RF plasma, wherein said exposure of said upper surface ofsaid wafer to said RF plasma renders said first silicon area suitablefor epitaxial silicon growth; growing epitaxial silicon on said firstsilicon area subsequent to said exposure of said upper surface of saidwafer to said RF plasma, wherein: said epitaxial silicon grows at alateral growth rate and a vertical growth rate; said lateral growth rateof said epitaxial silicon is reduced relative to said vertical growthrate by said exposure of said upper surface of said wafer to said RFplasma; and said lateral growth rate has a ratio to said vertical growthrate of between about 1:1 to about 1:8.
 22. The method as claimed inclaim 21 wherein said lateral growth rate has a ratio to said verticalgrowth rate of between about 1:4 to about 1:8.
 23. A method of growingepitaxial silicon, comprising: providing a wafer, wherein: said waferhas an upper surface; said wafer has a first silicon area on said uppersurface; and said wafer has a first dielectric area on said uppersurface adjacent to said first silicon area; forming a RF plasma from agas flow, wherein said gas flow comprises at least one etchant gas;exposing said upper surface of said wafer to said RF plasma, whereinsaid exposure of said upper surface of said wafer to said RF plasmarenders said first silicon area suitable for epitaxial silicon growth;growing epitaxial silicon on said first silicon area subsequent to saidexposure of said upper surface of said wafer to said RF plasma, wherein:said epitaxial silicon grows at a lateral growth rate and a verticalgrowth rate; and said lateral growth rate of said epitaxial silicon isreduced relative to said vertical growth rate by said exposure of saidupper surface of said wafer to said RF plasma, such that lateral growthof said epitaxial silicon is reduced over said first dielectric area.24. A method of growing epitaxial silicon, comprising: providing awafer, wherein: said wafer has an upper surface; said wafer has a firstsilicon area on said upper surface; said wafer has a first dielectricarea on said upper surface adjacent to said first silicon area; and saidfirst dielectric area has a surface; forming a RF plasma from a gasflow, wherein said gas flow comprises at least one etchant gas; exposingsaid upper surface of said wafer to said RF plasma, wherein saidexposure of said upper surface of said wafer to said RF plasma renderssaid first silicon area suitable for epitaxial silicon growth; saidexposure of said upper surface of said wafer to said RF plasmapassivates said surface of said first dielectric area; selectivelygrowing epitaxial silicon on said first silicon area subsequent to saidexposure of said upper surface of said wafer to said RF plasma, wherein:said epitaxial silicon growth on said first dielectric area is reducedby said exposure of said upper surface of said wafer to said RF plasma;said epitaxial silicon grows at a lateral growth rate and a verticalgrowth rate; and said lateral growth rate of said epitaxial silicon isreduced relative to said vertical growth rate by said exposure of saidupper surface of said wafer to said RF plasma.
 25. A method forselectively growing epitaxial silicon, comprising: cleaning a surfacehaving a dielectric area and a silicon area with a RF plasma formed froma gas flow having an etchant gas; and growing epitaxial silicon on saidcleaned surface, wherein: said epitaxial silicon growth exhibitsselectivity of growth on said silicon area over said dielectric area;and said selectivity of growth is enhanced by said cleaning of saidsurface.
 26. A method for reducing lateral growth of epitaxial silicon,comprising: cleaning a surface having a dielectric area adjacent to asilicon area with a RF plasma formed from a gas flow having an etchantgas; and growing epitaxial silicon on said cleaned surface, wherein:said epitaxial silicon grows at a lateral growth rate and a verticalgrowth rate over said silicon area; and said lateral growth rate of saidepitaxial silicon is reduced relative to said vertical growth rate bysaid cleaning of said surface.
 27. A method for growing epitaxialsilicon, comprising: cleaning a surface having a dielectric areaadjacent to a silicon area with a RF plasma formed from a gas flowhaving an etchant gas; and growing epitaxial silicon on said cleanedsurface, wherein: said epitaxial silicon growth exhibits selectivity ofgrowth on said silicon area over said dielectric area; said selectivityof growth is enhanced by said cleaning of said surface; said epitaxialsilicon grows at a lateral growth rate and a vertical growth rate oversaid silicon area; and said lateral growth rate of said epitaxialsilicon is reduced relative to said vertical growth rate by saidcleaning of said surface.